Emerging treatment patterns and checkpoint inhibitor (CPI) use among newly diagnosed Merkel cell carcinoma (MCC) patients in the United States veteran population.

Abstract

139 Background: MCC is a rare and aggressive skin cancer with annual incidence of 2,500 in the U.S. Checkpoint inhibitors (CPIs) demonstrated durable disease response historically not seen with chemotherapy among MCC patients in clinical trials. Avelumab, a PD-L1 antibody, became the first and only approved treatment for metastatic MCC by the U.S. FDA in March 2017. This study evaluated emerging treatment patterns among MCC patients using the US Veterans Health Administration (VHA) database. Methods: This retrospective study identified newly-diagnosed MCC patients who initiated ≥1 systemic therapy from Oct. 2013 to Jan. 2018 and had continuous enrollment from ≥6 months pre-initial MCC diagnosis date until ≥2 months post-index date with follow-up until the earliest of death, disenrollment, or study end. The index date was defined as the start date of first-line (1L) systemic therapy. A subsequent line of therapy (2L) was defined by the earliest of new therapy addition, regimen switch, or a new/existing regimen after a >60-day gap from the prior cycle end. Duration of 1L therapy was evaluated among patients treated with CPIs, National Cancer Comprehensive Network (NCCN)-recommended chemotherapy (recCTs), and other chemotherapy (oCTs). The median duration of therapy was estimated using the Kaplan Meier method. Results: Of the 120 MCC patients (72% pre-2017) with 1L systemic therapy, 17%, 45%, and 38% were treated with CPIs, recCTs and oCTs, respectively. More than 75% were white men aged ≥65 years with mean baseline Charlson comorbidity index scores ≥5. Carboplatin-etoposide (56%) and cisplatin-etoposide (26%) were the most commonly-used recCTs. The median duration of 1L therapy in patients treated with CPI, recCTs and oCTs was 300, 91, and 21 days, respectively. 2L therapy was initiated in 33% of all 1L patients. Conclusions: Among 1L MCC patients, CPIs treated patients appear to be on treatment longer than both recCTs and oCTs patients. These descriptive findings provide important insights into the emerging real-world treatment patterns amongst MCC patients in the VHA population.